Finding the Fourth Proportional to 99.71, 137.20 and 91.61

Step by Step Solution

1. Step 1: Write the proportion equation
   99.71 : 137.20 = 91.61 : x
2. Step 2: Convert to fraction form
   99.71/137.20 = 91.61/x
3. Step 3: Cross multiply
   99.71x = 137.20 × 91.61
4. Step 4: Simplify right side
   99.71x = 12,568.89
5. Step 5: Solve for x
   x = 12,568.89/99.71
6. Step 6: Final answer
   x = 126.05